Sword of the Underworld
by Lord Maximus
Summary: (One-shot based on Heaven's Star) Grim offers Numbuh 1 a way to save the Kids Next Door and the world from Mandy by giving him the power of ancient warriors who existed since the near beginning of time.
**A boy...**

A boy who was bald and wearing sunglasses.

 **A spirit...**

A skeleton wearing a black robe and holding a scythe.

 **Both the only hope for the world they live in...**

Images of monsters, ghosts, and evil looking humans glared at the boy and the skeleton.

 **The only way to save the world is to work together...**

They were now shaking hands while floating in a blue void.

 **The power that allows a heart to beat shines as bright as a star until it reaches its end...**

A bright light appears in the boy's chest and the sound of a heart beating was heard.

 **And burns out...**

The light vanished and the heart beat ceased.

 **The power of the living taken without a sound...**

A dark figure appeared behind the boy, its arms spread out like dark wings.

 **And the visitors return to the hidden world...**

Xxx

Nigel Uno watched from his holding cell as Mandy's ship left for Earth.

"Well, isn't this just the perfect Sunday?! First I'm stuck impersonating some half-wit kid, then a maniacal girl takes over the Kids Next Door and now I'm locked in a cell with some guy in a Halloween costume!" Numbuh 1 complained turning to his equally annoyed cell mate.

"It's not a costume! I am the Grim Reaper, and you have no idea of the power I possess." Grim replied.

"Oh, well why don't you use your 'power' to open the door and get us out of here?" Numbuh 1 gestured to the door.

Just then they both looked and saw the door open. Numbuh 1 looked to Grim, wondering if he did it but Grim simply shrugged, as clueless as he was on how the door was opened.

"Numbuh 1!"

Numbuh 1 turned around to see his best friend and second in command, Numbuh 5 run in wearing a simple green hospital gown.

"Man am I glad to see you! Everybody's gone crazy around here!" Numbuh stopped and looked at Grim before turning back to Numbuh 1 and lowered her voice. "And what happened to that guy? Don't they feed prisoners around here anymore?"

"Never mind him, let's go!" Numbuh 1 said.

They both ran for the door but stopped when Grim called out to them. "Wait! Take me with you, I can help!"

"With what? A crash diet plan?" Numbuh 5 asked.

"Hold on." Numbuh 1 walked up to Grim. "Why would you help us?"

"Because I am sick of everyone and their Aunt Trixie always taking my scythe! And I have especially had it with Mandy and her bossiness!" Grim replied. "But...there is a way to save your friends and for me to dissolve the deal I made with her."

"What is he talking about?" Numbuh 5 asked.

"Yeah, what are you talking about?" Numbuh 1 echoed Numbuh 5's question. "What deal?"

"I lost a bet with her and ended up stuck as her best friend/slave forever but that doesn't mean I haven't been looking for a way to dissolve the bet and it just so happens that now is the perfect chance, with Mandy and Billy going too far in their adventures they might actually disrupt the balance. Unfortunately by the time help arrives it'll be too late so I am stuck with you." Grim pointed at Numbuh 1. "I may be powerless without my scythe but I am still the Grim Reaper and I know a way to make the both of us powerful enough to fight both the Delightful Reaper and Mandy. I'll get my scythe and you'll get your friends back."

"Forget that fool, let's go!" Numbuh 5 grabbed Numbuh 1's shoulder.

"No." Numbuh 1 shook his head and looked at the surprised Numbuh 5. "Right now we need all the help we can get. You go find Numbuh 362, Abby. Grim and I will take care of everything planet side."

"Well then you'll need these." Numbuh 5 smiled as she pulled out his sunglasses, having successfully stolen them from Mandy when she had shed her Numbuh 1 disguise.

"Right, let's do it." Numbuh 1 put them on.

"Sunglasses? Are you going to a fight or a fashion show?" Grim asked.

"Just get on with it!"

"Very well."

Grim reached out and touched Numbuh 1's head and Numbuh 1's vision was clouded with images of battles throughout history, people fighting against what looked like monsters! A bright blue aura surrounded both of them, bright enough Numbuh 5 had to cover her eyes. A blue circle with runes appeared underneath Grim and Numbuh 1 and spread out, casting a blue light over everything and Numbuh 5 was left unable to move, seemingly frozen in time.

"Nigel Uno, I, the Grim Reaper, offer you the power to save your friends and the world. Do you wish to save them?" Grim asked.

"Of course!" Numbuh 1 shouted.

"Even if it means being forced to possibly give up your life?" Grim asked.

"What?!" Numbuh 1 exclaimed.

"Power comes at a price, boy, and if you accept the terms of my contract you become something completely different from a normal kid. You'll live and anyone who knows you will remember you but at the very same time your life will never be the same again." Grim responded. "Now, I will not ask again, do you wish to save everyone?"

The power to stop Mandy and the Delightful Reaper at the cost of his life being changed forever? It sounded crazy but Numbuh 1 was no stranger to things considered insane by normal people. He made up his mind; if his friends and family were safe and sound he didn't care.

"I want to save everyone." Numbuh 1 answered.

"Good, now we form the contract." Grim held out his hand, as if to shake Numbuh 1's. "Hold your hand."

Numbuh 1 slowly reached out and grasped Grim's hand. He gasped as a ball of fire came out of Grim's chest; the flames seemed to be as black as the endless void of space itself. Something he felt forced him to look down and gasp as a string of blue light came out of his chest and wrapped itself around the floating ball of black fire. The black flames traveled down the string and into Numbuh 1's chest.

He let out a cry as the black flames entered his body.

"The contract has been made and accepted." Grim laughed. "Oh I forgot to mention, this might hurt a bit."

A stream of black fire came out of Grim's body as his form started to disappear while the black flames enveloped Numbuh 1 who felt power coursing through his body and it hurt. As he yelled a pillar of black fire shot out from the ground, consuming him. The black flames shot up and hit the ceiling but oddly enough left no scorch marks when it was faded. The blue seal faded along with the blue light, unfreezing Numbuh 5.

"Numbu..." Abby lowered her hands to see what had happened only to see she was alone. "Numbuh 1?"

The cell was empty, which was supposed to be impossible because they were right in front of her just a second ago!

Xxx

Meanwhile the battle on the surface of Earth was not going well. Mandy's robot, the MANDROBOT was ineffective against the monster it was fighting no matter what attack or strategy it used. The monster was called the Delightful Reaper, a monster created when the Delightful Children from Down the Lane and Billy were caught in a Delightfulization Chamber, the same machine that created the Delightful Children. When it was activated, the resulting energies fused them together into a monster with the powers of the Grim Reaper and the hive mind of Delightful Children, even though Billy had still retained a bit of free will. The monster went on to absorb more children into it, a terrible fate as the children lost almost all free will as their minds and souls fused with it.

Mandy, after taking over the Kids Next Door had ordered the creation of a robot built in her image to fight it but the Reaper was almost unstoppable.

"YOU WILL ASSIMLA..." The Delightful Reaper stood over the MANDROBOT but stopped when something caught the attention of both sides.

A blast of black fire erupted between them and formed a pillar that shot up into the sky. Both combatants stopped and turned to the blast of black fire.

"What is that?" Mandy asked. "Get me a scan!"

"Scans coming in, that thing's power is off the charts! I gotta get a few more charts!" Numbuh 4 ended up buried in a huge pile of charts coming out of the computer.

"Ohh!" Billy's voice came from the Delightful Reaper. "Is it the fourth of the July already?"

The pillar of black fire faded revealing a gigantic skeleton wearing samurai armor and helmet with a skull shield in one hand and a giant sword in the other. The skeleton samurai wore a skull like mask with its mouth opened and showing nothing but a black void.

"Grim..." Mandy crossed her arms. "Guess I can't complain that he's doing something useful about this."

A blue seal appeared beneath the Skeleton Samurai and spread out; engulfing everything in a blue color and everyone but the Samurai, the Reaper, and the MANDROBOT was seemingly frozen in time like before on the Moonbase.

 **"Hey!"** The samurai pointed at the Delightful Reaper, its voice was a mix of Numbuh 1 and Grim's voice. **"You with the pants! We have come for the scythe and to save the world!"**

"And I've come for the all you can eat pancake breakfast!" Billy's voice shouted from the Reaper, earning a moment of silence. "But since there's no pancakes... RRRAHHHH!" The Delightful Reaper charged forward.

The Skeleton Samurai charged forward and both titans slammed into each other, grappling with equal strength. The Reaper swung its scythe and the Skeleton Samurai defended by raising its shield and blocked the scythe while it slammed the blunt end of its sword into the Reaper's side, making it stagger back from the blow. The Delightful Reaper regained its footing and swung its scythe again. The Skeleton Samurai raised its shield blocked the blow, even though its feet slid back a few inches.

The Reaper swung its scythe again, slamming into the skull shield and pushing the Skeleton Samurai back. The Samurai pushed forward and kneed the Reaper in the gut and slammed the blunt end of its sword into the Reaper's head, sending it spinning to the ground. The Delightful Reaper groaned and growled angrily before Billy momentarily took over. "Oooh! A bacon sandwich!"

The Reaper reached down and picked up the sandwich and fed it to Billy's skeletal face. "Hmmm, delicious!"

"Will you knock that off?! We have a battle to win!" The rest of the children composing the Delightful Reaper shouted as it got back up. "No more distractions!"

The Reaper spun around and swung its scythe, releasing a blast of energy that slammed into Skeleton Samurai's chest and knocked it down. The Delightful Reaper laughed and it stood over the Samurai.

"ASSIMILATE!" It swung its scythe down.

The Samurai raised its shield and blocked the scythe from hitting it.

 **"Hurry, Numbuh 1, before it gets us!"** Grim's voice shouted.

 **"Right, on three..."** The Skeleton Samurai rolled out of way as the Delightful Reaper brought its scythe down. **"One..."**

 **"Two..."** It kept on rolling until it far enough to get back up. **"Three! Cone of Bone!"**

The Samurai pointed its sword and fired a stream of bones that slammed into the Reaper, making it stagger back but it wasn't hurt at all!

 **"Our attacks are not working!"** Numbuh 1 exclaimed before Grim's voice took over. **"It's those pants! I know those pants!"**

Xxx

(Flashback)

"Yep, these are my lucky pants." Billy's dad, Harold pointed at his orange pants.

He and Grim were sitting on the couch with Harold reading the paper and Grim leaning on the far end of the couch with a single hand to keep his head up, miserably trying to watch TV and blot out Harold's voice.

"I wore these the night I got engaged to Gladys." Harold continued.

"You call _that_ lucky?" Grim asked incredulous.

"Heck no, they're lucky because they're immune to lasers, supernatural energies, and mustard." Harold went back to reading his paper.

Grim in the meantime acted like he hadn't heard a word.

(End Flashback)

Xxx

"ASSIMILATE!"

The Delightful Reaper swung its scythe down and the Samurai barely blocked with its shield.

 **"It's too...strong!"** Grim and Numbuh 1's voices groaned.

"ASSIMILATE!"

The MANDROBOT stepped forward and walked up to the Reaper.

"ASSIMILATE!"

 **"Mandy, you're our only hope! You have to pants the Reaper! It's the only way to defeat it!"** The Samurai called out.

"I have a better idea." The robot replied.

It tapped it on the shoulder and the Delightful Reaper spun around,

 **"Mandy, what are you doing?!"** The Samurai shouted as the Reaper swung its scythe and bisected the robot.

The Reaper laughed as it absorbed Numbuh 4, Numbuh 3, and Mandy into its being.

"Yes, this is power! Now I can finally rule the WORLD!" The Reaper turned around, only now its face resembled Mandy's.

It was obvious that Mandy had fused with the Reaper but her dangerous mind and heartless soul had allowed her to become the dominant personality of the Reaper bringing the minds of all children, even Billy under her control. The Skeleton Samurai stood up with its sword held in a ready position.

 **"So, you fused with the Reaper."** The Samurai stated.

"Yes, you puny KND are nothing compared to what I have become!" The Mandy Reaper declared. "I shall spread out and assimilate everyone on this world, gaining all the power and knowledge I need to spread out and take control of the UNIVERSE!"

 **"THAT SHALL NOT HAPPEN!"** The Samurai called out, Numbuh 1 and Grim's voices shouting so loud it echoed across the planet.

"You may want to surrender, Grim. You are useless without your scythe." The Mandy Reaper raised the scythe, ready to slice the samurai in pieces.

 **"You are right about one thing, Mandy, my scythe is da main source of my powers but I have a spare."** The Samurai spoke, Grim's voice sounding louder than Numbuh 1's. **"And you have finally pushed da boundaries far enough."**

"What are you talking about?" The Mandy Reaper demanded.

 **"I have been waiting for dis day ever since I first began formulating a plan to dissolve our bet and dat day has come. You have gone and fused with a monster composed of millions of children in your mad quest to take over the world, but even if we cannot destroy what you have become we can still seal you away."** The Samurai replied pointed its sword at the Reaper. **"Now dat you have dropped your guard I can use da special Method and tool that was created just for the occasion."**

"And what do you think has the power to stop me?" The Mandy Reaper scoffed. "I am now indestructible."

 **"No, you have allowed your original body to be turned into nothing but a form of energy that was absorbed into the Reaper along with your soul, leaving your mind intact and even allowed your higher level of intelligence to become the dominant personality."** The Samurai got ready to fight. **"Come at me, Mandy and you shall see what I mean before I seal you forever!"**

"With pleasure!" The Mandy Reaper charged forward with a roar.

The Samurai swung its sword the Reaper blocked...or it thought it did. It passed through the scythe and the Reaper's body like a ghost but the Reaper let out a scream.

"What?! What is happening?!" It cried out as a stream of blue energy came out of its chest and into the sword.

 **"The Blade of the Undead cannot cut anything in the living world, but when you became part of the Delightful Reaper you become a form composed of life energy."** The Samurai replied as an astral projection of Mandy was pulled out of the Reaper. **"Life Energy, the batteries of the living, just as important as the heart that pumps the blood in your bodies. I was almost afraid that this day would never come."**

"What are you talking about?" The astral projection of Mandy demanded.

 **"I was afraid you'd use science, not supernatural powers, to become what you've always wanted, an immortal being of unlimited power but it seems Lady Luck is finally on my side!"** The Samurai laughed. **"A monster created from my scythe, a boy with da strength and will to stand up against you, and da contract dat would give me the power I needed to seal you away forever."**

"YOU CAN'T DO THAT! YOU REMEMBER OUR BET, I OWN YOU!" Mandy shouted.

 **"True and I never go back on my word so I won't send you to the Underworld where a monster like you belongs. I kept my word with Jack O Lantern, he still has his eternal life and you shall have the life you want."** The Samurai pointed at her. **"Only dat it shall be from your own mind that your desires are granted."**

The Samurai's sword glowed bright blue and a bright beam of energy reached out and grabbed Mandy, pulling her towards the sword.

"YOU'LL PAY FOR THIS GRRRRRIIIIIIMMMMM!" Mandy was pulled into the sword her voice echoing as though she was falling off a cliff.

The blue aura surrounding the sword faded and Mandy's voice was silenced, gone from this world.

 **"Not likely, anyone caught in da blade is left to be forever trapped in a dream world. Spend the rest of eternity dreaming of your world domination."** The Samurai looked to the Reaper as its face changed back to resembling Grim's. **"As for da rest of you..."**

The Samurai jumped into the air above the Reaper. **"SWORD OF BONE!"**

Combining the sword's special power along with its most powerful attack it sliced its sword down the Delightful Reaper, earning a shriek of pain as it fell over. Streams of light blasted out of its face and landed on the ground, changing into the children that had been absorbed by the Delightful Reaper. What remained of the Reaper was its robe and pants as it collapsed, all the children that made up its being gone. The scythe spun through the air until it landed in the hands of its rightful owner.

 **"Finally, my scythe!"** Grim's voice said victoriously.

The Skeleton Samurai vanished in a flash of blue light.

Xxx

The Moonbase had returned to its normal form with Mandy and her control over the organization now gone.

"Excellent work, Numbuh 1, you destroyed the Delightful Reaper and stopped Mandy." Rachel T. McKenzie AKA Numbuh 362 congratulated. "Just what happened to Mandy anyway?"

Numbuh 1, Nigel Uno was now back in his regular clothes rubbed the back of his head. "Well...that's a good question. All I know is that she's somewhere where she can't cause any more trouble."

"Never the less, good job. Who knows what could have happened if Mandy had succeeded." Rachel nodded.

"HIDE ME!"

Billy ran up and hid behind Numbuh 1 as his dad came out. Numbuh 1 quickly moved out of the way, thankful he had changed back into his normal clothes while Billy screamed when his cover had moved and his dad spotted him.

"You are in big trouble mister!" Harold ran up and grabbed Billy's ear. "Nobody wears the pants but me!"

"Quick, call the Powerpuff Girls! Grim! Mandy! Help me!" Billy shouted as he was dragged off.

"Man, that Billy was crazy." Numbuh 3 said.

"Totally." Numbuh 362 nodded.

Nigel nodded, happy that Mandy was defeated but knew deep down he had other things to worry about. As he finished his report he walked towards the exit and noticed something. It was a black book, a book he had left when he came to deliver his report. He picked it up and walked towards the hangar.

He did not notice Numbuh 5 watching him as he left.


End file.
